1. Field
Example embodiments relate to a method of manufacturing crystalline silicon (Si), and more particularly, to a method of manufacturing crystalline Si using a plasma process.
2. Description of the Related Art
A representative method of growing crystalline silicon (Si) includes a capacitive coupled plasma (CCP) method using a showerhead or a hot-wire chemical vapor deposition (CVD) method using a metal material, e.g., tungsten (W).
The CCP method corresponds to a plasma process for applying a radio frequency (RF) bias to a showerhead and performing deposition by diluting an Si material, e.g., SiH4, in an environment having a relatively large amount of H2. The hot-wire CVD method is a method of supplying a current to a metal wire, e.g., a W wire, and performing deposition by decomposing a reaction/material gas, e.g., SiH4, due to catalysis of W at high temperatures.
In the hot-wire CVD method, due to the temperature of a metal wire separated from a substrate, deposition is performed regardless of the temperature of the substrate, and thus, low deposition temperature may be induced. However, because a process reproducibility problem and a cleaning problem occur due to the accumulation of an impurity, e.g., Si, deposited on the metal wire itself, the hot-wire CVD method may not be easily applied to a mass production process.
Currently, a plasma method of applying an RF bias to a showerhead and diluting an Si material, e.g., SiH4, is used in the mass production process. However, the existing plasma method may not easily achieve crystalline characteristics of Si due to an amorphous Si (a-Si) layer formed in an early deposition process due to an Si thin film being actually deposited on an oxide or nitride film that is mostly amorphous. Therefore, early Si nucleation may not be performed easily, the mobility of Si nuclei is reduced, and thus, a stable lattice structure may not be formed easily. In general, crystallization is performed and crystalline Si is obtained after an amorphous portion greater than about 1000 Å is formed. Thus, because a double layer of a-Si/crystalline Si is formed in most cases, a crystalline Si layer is not formed to a desired thickness at high speed and improved mobility and a low defect density may not be easily achieved.